Stabilized trichloroethylene

ABSTRACT

A phenol which carries at least one substituent in an ortho position with respect to a hydroxy-group and phenol itself or a substituted phenol which carries no substituent in an ortho position with respect to a hydroxy-group are used as synergistically co-operative inhibitors of oxidation of trichloroethylene.

tates Patent Campbell et a1.

[451 July 11, 1972 [54] STABILIZED TRICHLOROETHYLENE [72] Inventors:Alastair Campbell; Peter Robinson, both of Runcorn, England [73]Assignee: Imperial Chemical Industries Limited,

London, England 22 Filed: Feb. 20, 1970 21 App1.No.: 13,203

[30] Foreign Application Priority Data March 24, 1969 Great Britain..l5,306/69 [52] US. Cl. ..260/652.5 R, 252/170, 252/171, 252/403 [51]Int. Cl ..C07c 17/40, C07c 17/42 [58] Field of Search ..260/652.5;252/170, 171, 403

[5 6] References Cited UNITED STATES PATENTS 3,000,977 9/1961 Patron eta1. ..260/652.5 2,751,421 6/1956 Stauffer ...260/652.5 3,293,312 1/1966Ryckaert et a1 ..260/652.5

2,008,680 7/1935 Carlisle et al. ..260/652.5 3,076,040 1/1963 Skeeters....260/652.5 3,539,646 11/1970 Dannels et a1. ....260/652.5 X 2,947,7928/1960 Skeeters ....260/652.5 3,230,175 1/1966 Martens ....260/652.52,981,760 4/1961 Ferric et al. ....260/652.5 3,326,989 6/1967 Cormany eta1. ..260/65 2.5

FOREIGN PATENTS OR APPLICATIONS 422,406 3/1965 Japan ..260/652.5

1,083,698 9/1967 Great Britain ..-...260/65 2.5

Primary ExaminerHoward T. Mars Attorney-Cushman, Darby & Cushman [57]ABSTRACT trichloroethylene.

3 Claims, No Drawings STABILIZED TRICHLOROETHYLENE The present inventionrelates to stabilized trichloroethylene. More particularly it relates toa method of inhibiting oxidative decomposition of trichloroethylene.

It is known that trichloroethylene tends to decompose by atmosphericoxidation with the progressive formation of acidic products,particularly under the influence of heat and light. It is also knownthat in the presence of reactive metals, notably aluminum, the solventcan undergo a self-condensation reaction, leading to rapid discolorationand ultimately the formation of tarry material and copious amounts ofacid products. When the solvent is employed for the treatment of textilefibers and fabrics, as for instance in scouring and desizing operationsduring textile manufacture and in dry-cleaning of finished textiles,metal-catalyzed decomposition is not usually a problem but long-termprotection against oxidative degradation of the solvent is essential,particularly since the solvent used in these processes must berepeatedly recovered for reuse.

It is known to suppress oxidative deterioration of trichloroethylene byadding an inhibitor to the solvent, particularly a phenolic compound,for instance phenol itself, cresol, thymol, ptert.-butyl phenol,p-tert.-amyl phenol or isoeugenol. When the stabilized solvent is usedfor the treatment of textile materials it is desirable to keep theconcentration of phenolic additives as low as possible because residualodor can be imparted to the textile material by phenols adsorbed thereonfrom the solvent. We have now found that a synergistic antioxidanteffect can be obtained by adding to trichloroethylene a phenoliccompound from each of two distinct classes of phenolic compounds. Byworking in this way an equivalent antioxidant effect can be obtainedwith a smaller total concentration of phenolic compounds than using onephenolic compound alone, or alternatively a higher degree of resistanceto oxidation can be achieved with the same total concentration ofphenolic compounds.

According to the present invention, therefore, we provide a stabilizedtrichloroethylene composition which comprises trichloroethylene and assynergistically co-operative inhibitors of oxidation thereof asubstituted phenol which carries at least one substituent in an orthoposition with respect to a hydroxygroup and phenol itself or asubstituted phenol which carries no substituent in an ortho positionwith respect to a hydroxygroup the amount of each of the said phenolsbeing in the range 0002-! .0 percent by weight ofthe trichloroethylene.

in each class ofsubstituted phenols as defined in the precedingparagraph the substituent atoms or groups may be any of chloro, nitro,alkoxy, hydroxy, amino, alkylamino, keto, alkanoyl, alkyl, alkenyl,aryl, and substituted alkyl, alkenyl and aryl wherein the substituentsare any of chloro, nitro, alkoxy, hydroxy, amino, alkylamino, keto andalkanoyl. So that the inhibitors will vaporize readily with thetrichloroethylene during distillation of the solvent it is preferredthat the substituents be small. It is also preferred that the inhibitorsshould have a low solubility in water so that they remain substantiallyin the solvent phase when the solvent has been recovered by steamdistillation after use. Most preferably the phenols employed contain notmore than one substituent in the benzene ring in addition to the parenthydroxy-group, since such phenols are more readily recovered along withthe solvent during steam distillation. Suitably the substituents arestraight-chain or branched-chain alkyl and/or alkoxy radicals containingnot more than five carbon atoms each, but this is not essential.

In general we prefer to employ approximately equal parts by weight ofeach of the said two classes of phenolic compound. Proportions of eachclass of phenolic compound in the range 0.0l0.l percent, calculated onthe weight of the trichloroethylene, are most suitable.

If desired, within the scope of the invention, other materials known toexert an antioxidant effect in trichloroethylene may also beincorporated in the stabilized solvent, for instance one or more ofalkyl butenes, alkyl butadienes, amines, pyrrole, substituted pyrroles,hydrazines, hydrazones and oximes. Suitable amounts of any of thesematerials are for example 0.00052 percent by weight. An acid acceptorsuch as an epoxide, particularly the butene oxides and/orepichlorhydrin, may also be included in the stabilized solvent. Suitableamounts of epoxide are for example 0.1-1 percent by weight. Furthermore, if it is desired also to give the solvent extra protectionagainst decomposition in the presence of reactive metals such asaluminum, one or more of the known inhibitors of this type ofdecomposition may be included, for instance one or more of alcohols,ketones, carboxylic esters, nitroalkanes, alkyl and alkoxy esters ofnitric acid, alkyl and aralkyl ethers, and cyclic ethers containing morethan two carbon atoms in the ring. Suitable amounts of any of thesematerials are for example 0.1-2 percent by weight.

The invention is further illustrated by the following comparativeexamples in which the effect of incorporating a single phenol intrichloroethylene is compared with the effect of incorporating twophenols in accordance with the invention at the same total phenolconcentration in preventing oxidation of the solvent in the presence ofheat and light. The tests were also conducted in the presence of ironpowder since solvent used only for the treatment of textile materialsand other applications where contact with aluminum and very reactivealuminum alloys is not a problem is nevertheless likely to come intocontact with iron in the structural members of the treatment plant. Allpercentages are by weight calculated on the weight of thetrichloroethylene.

EXAMPLES One hundred and eighty ml of trichloroethylene with or withoutadditions of phenols, as shown in the following table, and no otherstabilizers were placed in a 500 ml conical flask together with 1.5g ofiron powder. The flask was placed on an electric hot-plate with itsvertical axis 4.5 inches from the center of an watt Mazda mercury lightbulb suspended vertically with its lower end 2 inches above the level ofthe top of the hop-plate. A soxhlet extractor surmounted by adoublesurface condenser and modified to act as a water-separator andgive a continuous feedback of refluxing solvent to the flask was fittedto the main neck of the flask and 20 ml of the same trichloroethylenesample as in the flask were placed in the soxhlet extractor and coveredwith 40 ml of distilled water, taking care to avoid any water enteringthe flask or the feedback arm. A dip-tube for the admission of oxygen tothe liquid in the flask was fitted to a side neck.

A flow of oxygen (two bubbles/second) was passed through the solvent andthe heat was switched on. When the solvent was refluxing at a steadyrate the lamp was switched on and the test was continued for 18 hours.The lamp and heater were then switched off, the flask was allowed tocool and the oxygen flow was stopped. The results of the tests wereevaluated by measuring the total chloride ion formed by decomposition ofthe solvent. This was done by washing out the condenser with distilledwater, adding the washings to the aqueous layer separated from thecontents of the soxhlet extractor and titrating the total aqueous phasefor chloride ion, then combining the solvent layer from the soxhletextractor with the solvent in the flask and determining the totalchloride ion in the solvent phase by titrating 50 ml of the solventphase while stirring vigorously with 200 ml of distilled water. Theresults of the two titrations were combined, a blank figure for anychloride ion found in the distilled water used being subtracted. Theresults shown in the following table demonstrate the synergistic effectof employing two classes of phenolic compound together as inhibitors inaccordance with the invention.

phenol p-tert.-amyl phenol What we claim is:

1. A stabilized trichloroethylene composition consisting essentially oftrichloroethylene and as synergistically co-operative inhibitors ofoxidation a combination of phenols which consists essentially ofmonosubstituted monohydroxy phenol which carries only one substituent inan ortho position with respect to the hydroxy-group and phenol itself ormonosubstituted monohydroxy phenol which carries only one substituent inother than the ortho position with respect to the hydroxy-group, whereinthe substituents of the substituted phenols are alkyl and/or alkoxyradicals containing not more than five carbon atoms each, the amount ofeach of the said phenols being in the range 0.002-l .0 percent by weightof the trichloroethylene.

2. A composition according to claim 1, wherein the amount of each of thesaid phenols is in the range 0.01-0.1 percent by weight of thetrichloroethylene.

3. A composition according to claim 1, wherein the amounts of each ofthe said phenols are approximately equal.

2. A composition according to claim 1, wherein the amount of each of thesaid phenols is in the range 0.01-0.1 percent by weight of thetrichloroethylene.
 3. A composition according to claim 1, wherein theamounts of each of the said phenols are approximately equal.